There are two sides to the question of which lights are better. The first one is "which lights are better FOR THE CORAL?", and the second is "which lights are easier for me?".
The first is by definition subjective, and can be debated endlessly, since we can't just ask the corals what they think. Well, I should say, we can ask them, we just can't hear their answer.
The second is pretty solid, and like most things, revolve around money. LED's are expensive up front, but use very little power, and their lifespan is measured in years at least, if not decades. They also run relatively cool, so they don't heat up the tank or the room significantly. So overall, the cost to operate is minimal.
MH lights are not cheap up front, especially if buying new, and the bulbs do deteriorate with use to the point that they require replacement regularly, but the biggest drawback is power consumption, both in terms of increased electrical bills, and in elevating the water temp, often to the point that it must be externally chilled, and requiring additional air conditioning to keep the room at a comfortable temp.
T5 lights can be set up for very minimal up front cost if you buy commercial type fixtures and retrofit them into a canopy or some such, and the heat output is much more manageable than MH. But most aquariums require multiple bulbs to reach desirable par values, and they are not cheap, plus they deteriorate quite rapidly and must be changed regularly. They do offer the ability to mix and match output spectrums and tailor the overall light to your personally preferred balance of visual interest and coral growth.
Somebody with more direct experience can hopefully chime in with some actual quantitative data for us.
